Invasive Plants in Northern Virginia: Japanese Stiltgrass

By Elaine Mills, Extension Master Gardener

Japanese Stiltgrass
Photo 2012 in NJ

One of more damaging invasive species in the Mid-Atlantic region, Microstegium vimineum, (Japanese stiltgrass) threatens wooded areas and is increasingly found on farms and in residential areas where it can invade lawns, landscape beds, and vegetable gardens. This native of China, Japan, and India was first documented in Tennessee in 1919 when it was thought to have been accidentally introduced through its use as packing material in shipments of porcelain.

Japanese Stiltgrass infestation – note the shiny, off-center mid rib
Photo © National Park Service

Japanese stiltgrass is an annual grass that germinates in late winter to early spring and grows to around 3 feet with thin, wiry, bamboo-like stalks. Its narrow, lance-shaped leaves have a distinctive silvery stripe of reflective hairs down the midrib of the upper leaf surface. It flowers from August to September and then dies back in the fall, producing a thick layer of smothering, dry, tan thatch that is slow to decompose.

Japanese stiltgrass exhibits a number of invasive characteristics. Its fast-growing stems allow it to climb over and shade out other vegetation by sprawling in a mat-like manner. It produces abundant sticky seeds — up to 1,000 seeds per plant — from both self- and cross-fertilization.  These are easily carried on the fur and hooves of animals or by water during heavy rains and can remain viable in the soil for five years. The plant also spreads through rooting of stem nodes that touch the ground. It tolerates full sun to shady conditions and can tolerate mild frosts, even flowering after the first frost in the fall.

Japanese Stiltgrass infestation spreading for acres in forest.
Photo © Michael Ellis

In forests, Japanese stiltgrass threatens plants in the understory. Overgrazing by deer on shrubs and saplings improves light conditions, allowing it to get a foothold. Because animals find it unpalatable, the plant spreads rapidly into extensive patches and displaces less competitive native species. Stiltgrass also inhibits tree growth by changing soil nutrient cycling processes. If unchecked, it can overtake native vegetation in three to five years.

A combination of cultural practices and mechanical and chemical controls can help homeowners deal with infestations. For details on management in landscape beds and lawns, see Rutgers University Cooperative Extension fact sheet at https://njaes.rutgers.edu/fs1237/


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